The world's industrial nations continue to rely very heavily on energy produced from oil. As the major oil producing countries are not the major oil users, a great deal of the world's oil production has to be transported by sea. Tanker numbers, and more especially tanker sizes, have increased significantly during recent years and this has resulted in an increase in the number and severity of tanker accidents. There have been several recent examples of the disastrous consequences of an uncontrolled oil spill.
The majority of tanker spills occur in port during loading/unloading operations and are contained by shore-based facilities.
Tanker oil spills at sea are presently also treated by shore-based facilities. This practice involves significant delays whilst the equipment is being mobilised and transported to the accident site. Such delays allow the oil spill to grow larger in both volume of oil spilt and in surface area, making the spillage, and hence damage, progressively more difficult to contain.
Current oil spill control methods include the use of dispersants to break up the slick, sinking agents to sink the oil to the sea bed and oil booms to contain the spill and allow, at least, partial recovery of the oil. It is generally agreed within the oil industry, however, the removal of the oil, if possible, is the best method for dealing with oil spills and to achieve this the oil must be contained.
While the economic value of oil recovered after an oil spill cannot be disregarded this often represents only a small proportion of the full financial loss in a major incident. By far the most costly effect is that of environmental damage. Clean-up operations following an oil spill accident are extraordinarily expensive and are seldom entirely effective. Much damage is usually done before the clean-up operation can be initiated; the operation is generally heavily labour intensive and the efforts are seldom better than token in saving wildlife immediately affected - both flora and fauna. Further, many of the world's most highly regarded tourist attractions border on the sea and tourism operators face heavy financial losses as a consequence of any oil damage to these attractions.
To contain oil spills from marine vessels, it is known to carry an oil slick barrier in folded form on board the vessel (e.g. an oil tanker) for deployment around the vessel in the event of an oil spill. An example of a vessel-borne oil slick barrier can be found in German patent document no. DE2923083, which describes a vessel having an on-board oil slick barrier stored in folded form in an enclosure around the outside of the tanker hull. The enclosure is formed by one or more curved flaps pivotally connected to the hull. Upon opening of the flap(s), the oil slick barrier is jettisoned and inflated from compressed air cylinders which act as ballast for the barrier.
However, the known oil spill containment system has several inherent disadvantages. First, the construction of the enclosure on the outside of the hull of a new ship, or retrofitting the enclosure to an existing ship, is prohibitively expensive. Secondly, the location of the enclosure on the outside of the ship's hull interferes with the docking of the ship. Thirdly, the enclosure is not sealed and is subject to salt water penetration, with consequent corrosion problems. Fourthly, the enclosure is opened by hydraulic cylinders which, in addition to being subject to corrosion, are not necessarily failsafe. Fifthly, the enclosure is not readily accessible for inspection and maintenance. Sixthly, the compressed air cylinders have a limited life and are subject to leakage. Finally, the oil barrier, once deployed and inflated, is subject to leakage and, once the gas in the cylinders has been exhausted, the barrier may sink.
It is an object of the present invention to provide an improved oil spill containment system which overcomes or ameliorates at least some of the disadvantages described above.